CTX-M-55-type ESBL-producing fluoroquinolone-resistant Escherichia coli sequence type 23 repeatedly caused avian colibacillosis in Kagoshima Prefecture, Japan.

OBJECTIVES: The production of expanded-spectrum beta-lactamases (ESBLs) and fluoroquinolone resistance in Enterobacteriaceae has become a global concern. The aim of this study was to investigate the spread of ESBL-producing and fluoroquinolone-resistant avian pathogenic Escherichia coli (APEC) in Kagoshima, a prefecture with the largest amount of poultry in Japan.

METHODS: The antimicrobial susceptibility and genetic characteristics of 228 APEC strains isolated from 57 farms in Kagoshima Prefecture, Japan, between 2005 and 2017 were analyzed. Information about the companies with hatcheries connected to the farms was also collected, and the epidemiological relatedness of APEC strains and the processes of adopting chicks were compared.

RESULTS: Seven CTX-M-type ESBL genes, blaCTX-M-1 , blaCTX-M-2 , blaCTX-M-14 , blaCTX-M-15 , blaCTX-M-25 , blaCTX-M-55 , and blaCTX-M-65 , were found in 60 (26.3%) of the 228 APEC strains. The ciprofloxacin-resistant strains belonged to 10 different sequence types (ST10, ST23, ST93, ST155, ST156, ST350, ST359, ST602, ST648, and ST9479), and the two ST602 strains showed remarkably high ciprofloxacin resistance (MIC: 128 µg/ml) and had amino acid mutations in GyrA (S83L and D87N), ParC (S80I), and ParE (E460A). A CTX-M-55-type ESBL-producing fluoroquinolone-resistant Og78-ST23 strain was isolated multiple times over two years on a farm. Furthermore, epidemiologically closely related strains were isolated from different farms that used the same common hatcheries.

CONCLUSIONS: APEC is often transferred from hatcheries to farms via healthy chicks, and the prudent use of antimicrobials and careful monitoring of resistant strains on poultry farms and hatcheries are important in preventing the selection and spread of high-risk APEC strains such as CTX-M-55-type ESBL-producing Og78-ST23.